When a young Japanese agronomist, Shinya Imahashi, started his small Natural Agriculture demonstration farm near Yatesbury in Wiltshire, he invited organic farmers to hear about the way he works. His visitors were interested, but they warned him that, unless he fed his soil or used rotation, within five years many of his crops would fail. Six years on, his vegetables are thriving and taste delicious. This is what Shinya Imahashi does: after sowing seeds he’s…